Optical readers are widely used in department stores, supermarkets and recently in cargo transportation systems to read the data on containers or tags and derive information about sales amount, inventory, or the destinations of goods to be transported. In a system called "Point of Sales", for instance, product information about the species, manufacturing lot and and price are printed on a merchandising tag in an optically readable form. The tag is read by an optical reader and the information obtained by the reader is sent to a computer system, which processes the information to provide a list of data.
However, the way of expressing the product data is not uniform. In department stores often the tags for foods and beverages have their data expressed in numbers and bar codes (the numbers being beneath the bar codes) while data on clothes is expressed in alphanumeric characters. Therefore, it has become necessary to install optical readers which are capable of reading both alphanumerics and bar code symbols.
U.S. Pat. No. 4,402,088 relates to a hand-held optical reader, i.e., a "scanner", which will read either a bar code or alphanumeric format without the operator having to manually switch between the two, depending upon which the unit is reading.
According to that patent, the hand-held reader produces electrical signals representative of data scanned from the document and processes the obtained data by two examination means concurrently. It produces an output representative either of alphanumeric characters or of bar codes, followed by gating out of one of the outputs of the two examination means, but not both of them.
In U.S. Pat. No. 4,402,088, McWaters et al, the same hand-held scanner reads either alphanumeric or bar code formats without operator intervention to switch from one to the other. Its method of reading the two formats, with the same scanner, is the same as the methods disclosed in its preceding published Japanese Patent Application No. 13307/77 (Feb. 9, 1977) of Saitoh, which is Publication No. 98733/78 (Aug. 29, 1978).
In the above-cited references, two signal processing means are used concurrently. The first processing means processes the binary signals obtained from the photoelectric elements to provide recognition results from characters. The second processing means processes the binary signals, obtained from the photoelectric elements, concurrently to obtain recognition results from bar codes.
In these references, the final recognition results are selected when they are meaningful. There is high possibility for the optical readers of these references to unnecessarily process the signals of a pattern which is neither character nor bar code, and this leads to occasional misreading of meaningless stains or spots on the surface of the document.